This subproject is one of many research subprojects utilizing the resources provided by a Center grant funded by NIH/NCRR. The subproject and investigator (PI) may have received primary funding from another NIH source, and thus could be represented in other CRISP entries. The institution listed is for the Center, which is not necessarily the institution for the investigator. The Alzheimer's Disease Neuroimaging Initiative (ADNI) is a 5-year NIA initiative to test whether serial magnetic resonance imaging (MRI), positron emission tomography (PET), other biological markers, and clinical and neuropsychological assessment can be combined to measure the progression of mild cognitive impairment (MCI) and early Alzheimer's disease (AD). ADNI will compare neuroimaging, biological and clinical information from study participants seeking correlations among the data that will track the progress of memory loss from its earliest stages. A total of 800 subjects will be recruited at 50 sites in the US and Canada. The subjects will undergo clinical and neuropsychological evaluations each time scanning is performed. All subjects will undergo repeated 1.5T MRI scanning, 25% will undergo repeated 3T MRI scanning, and 50% will undergo repeated PET scanning with the same frequency of scanning used for the 1.5T MRI imaging. What is learned from the study will be used to help researchers and clinicians develop new treatments and monitor their effectiveness, increasing safety and efficiency of medication development.